Important Info 0365 KB Articles

Exchange Hybrid Considerations
https://docs.microsoft.com/en-us/exchange/exchange-hybrid#considerations

Calendar data Cross Forest.
https://support.microsoft.com/en-us/help/3187044/can-not-view-cross-forest-calendar-data-in-office-365-hybrid

-Check Modern auth is enabled (legacy may cuase issues.)


Send As Perms
https://support.microsoft.com/en-us/help/3045224/can-t-send-an-email-message-when-full-access-permission-is-granted-to

Cant add room or resource mailbox in 0365 hybrid environment
https://support.microsoft.com/en-us/help/3161713/can-t-add-a-room-or-resource-mailbox-in-office-365-hybrid

GUID Info
https://support.microsoft.com/en-us/help/4051496/can-t-add-an-on-premises-mailbox-as-an-additional-mailbox-in-exchange


ACLAble
https://support.microsoft.com/en-us/help/4051497/a-remote-mailbox-created-in-on-premises-active-directory-is-not

Cant see free/busy after move to 0365
https://support.microsoft.com/en-us/help/3079929/users-cannot-see-free-busy-information

OWA & Delegates cant accept meeting requests.
https://support.microsoft.com/en-us/help/4089867/delegate-can-t-accept-meeting-request-when-manager-in-other-forest-dur

Delegates cant see correct calendar items
https://support.microsoft.com/en-us/help/4089865/delegate-can-only-see-free-busy-information-in-owa-when-manager-is-in

Exchangesync writeback info
https://docs.microsoft.com/en-us/azure/active-directory/hybrid/reference-connect-sync-attributes-synchronized#exchange-hybrid-writeback